Ink jet apparatus and ink jet print method having a plurality of double-sided printing modes

ABSTRACT

An ink jet print apparatus having a plurality of double-sided printing modes (e.g., automatic double-sided printing mode and manual double-sided printing mode) produces a sufficient image quality whichever mode is executed. For this purpose, image data to be printed is converted into print image data usable by the printing apparatus in a way that matches a selected one of multiple print medium transport paths. This minimizes a curling problem due to variations in transport processes, image quality variations caused by an ink fixing problem and adverse effects on the printing apparatus and ensures a stable printing whichever transport path is used for printing.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to an ink jet print apparatus, an ink jetprint method and a program for forming an image on a print medium byejecting ink from a print head according to print data.

2. Descrption of the Related Art

Office automation equipment such as personal computers and wordprocessors are in wide use today. A variety of printing apparatus andmethods have been developed to record information output from theseoffice equipment on various print media. There is a growing trend inoffice equipment for displaying video in color thanks to their improvedprocessing capacity. In line with this trend, more and more printingapparatus capable of recording information in color are being developed.

Printing apparatus capable of forming a color image vary widely in priceand function, ranging from low-cost devices with relatively simplefunctions to multifunctional ones that let user to select a desiredprint speed and quality according to the kind of an image to be printedand to its use. An ink jet printing apparatus in particular has found awide use, such as on printers, copying machines and facsimiles, becauseof its many features including low noise, low running cost, small size,and relative ease with which a color image can be formed.

Generally, a color ink jet printing apparatus forms a color image usingthree color inks, cyan, magenta and yellow, or four color inks furtherincluding a black ink. Many of them use an aqueous liquid containing acoloring material. Thus, for an ink to soak into a print medium and drythere takes a certain length of time. Therefore, not many printingapparatus have been available which can perform a high-speed printing.Now that a variety of uses have been emerging as described above, thereis a growing demand for a faster printing speed. In recent yearshigh-speed printing apparatus are on the market which can print morethan five, or even 10, A4-size sheets a minute.

Home-use ink jet printing apparatus are rapidly proliferating which canprint a user-designed image including photograph on a large number ofNew Year postcards continuously. A printing apparatus is also reachingthe market which can realize a so-called “full bleed printing” by whichan image is printed to the edges of a print medium.

When a large number of postcards are to be printed, a normal process isas follows. First, only an address side or a message side (where aphotograph or message is to be printed) of one or more cards is printed;and then the user turns over these cards and feeds them into theprinting apparatus for printing on their opposite side. This procedureis troublesome for the user and there is a possibility of the userinserting the cards in a wrong direction. To deal with this problem, aprinting apparatus has already been proposed which, as disclosed inJapanese Patent Application Laid-open No. 2000-191204, has an automaticreversing unit for automatically turning over sheets.

In the printing apparatus incorporating the automatic reversing unit,one side of the print medium is first subjected to an ordinary printing,after which the print medium is pulled back in the opposite direction tothe automatic reversing unit installed in the printing apparatus. Uponreceiving the print medium, the automatic reversing unit turns it overso that its unprinted side faces the printing unit then the print mediumis transported from the automatic reversing unit to the printing unit.The printing unit prints on the unprinted side of the reversed printmedium, which is then discharged from the printing apparatus. With theabove steps automatically executed, the address side and the messageside of a postcard can be printed in one process.

In the ink jet printing apparatus that performs the automaticdouble-sided printing, however, problems may arise during the transportprocess. They are explained as follows.

One of the problems is a curl of a print medium. Since the ink jetprinting apparatus generally uses aqueous inks, after plain paper or inkjet paper absorbs inks, paper fibers may contract curling the paper.Particularly when the above “full bleed printing” is performed or when asmall-sized postcard is printed with a plurality of color inks andtherefore with a large volume of inks, the print medium absorbs inks upto its edge, which makes the curl phenomenon more conspicuous. If thedouble-sided printing is performed on the curled postcard, when thepostcard is transported for the double-sided printing, ends of the cardmay be caught on parts of the automatic reversing unit or printingapparatus body, making it impossible for the card to be fed smoothlyinto the printing apparatus or the printing unit.

Further, since a fixing time of ink varies depending on the type ofprint medium and ink used and on ambient temperature and humidity,another problem arises from a failure to completely manage thesefactors.

In addition to printing high-quality photographic images on New Yeargreeting cards as described above, the user often prints simpledocuments and Internet web pages on plain paper on a daily basis.Actually, an appropriate kind of ink to be applied varies according tothe use. In printing a high-quality photographic image, it is generallyconsidered advantageous to use an ink composed mainly of a dye-basedcolorant with an excellent penetrability (hereinafter referred to as apenetrative ink). However, the penetrative ink is generally not vividwhen printed on plain paper and thus not so suited to printing simpledocuments on plain paper on a daily basis. In contrast to this, inkcapable of realizing a high-quality printing even on inexpensive plainpaper is said to be an overlay type ink that contains such a colorant aspigment. Unlike the penetrative ink, the overlay type ink, when it usesa pigment as colorant, has larger colorant particles than a dye ink andthus cannot easily penetrate deep into fibers of the print medium, withthe result that the colorant particles are more likely to stay on asurface layer of the print medium. Therefore, output images printed withthe overlay type ink have a higher optical density than those printedwith the penetrative ink. Further, since an ink penetration (spread) tothe surrounding area is also smaller than when the penetrative ink isused, image boundaries are clearly printed. On the downside, since thecolorant stays and becomes fixed near the surface layer of the printmedium, the printed surface tends to be rough. This means it has a lowerrubbing resistance than the penetrative ink. The degraded rubbingresistance gives rise to another problem that ink can easily come offeven with a slight friction. Another drawback of the overlay type ink isa longer fixing time required than that of the penetrative ink.

To make the most of the features of these inks, an ink jet printingapparatus has been proposed which uses both of the penetrative ink andthe overlay type ink (or dye ink and pigment ink). Such an ink jetprinting apparatus often uses a pigment-based overlay type ink for onlya black ink that is most consumed in document printing and dye-basedpenetrative inks for color inks (cyan, magenta and yellow inks includingthose of differing densities).

In such an ink jet printing apparatus incorporating inks with differentfeatures, when the above double-sided printing is performed, the inkfixing time for the first side of the print medium that is printed firstvaries depending on which ink is applied. If the print medium with theink on the first side not yet fully dry is transported to the automaticreversing unit and turned over, the printed surface on which the ink isnot yet fully fixed may directly come into contact with, and be rubbedby, inner mechanisms of the apparatus, causing many problems including asignificant degradation of the print quality or a smearing of the innermechanisms with ink. This in turn may lead to another problem of asecondary smear, in which the next print medium will be smeared by thecontaminated inner mechanisms. Although the ink kind is taken as anexample, the above problem similarly arises depending on the type ofprint medium used, ambient humidity and temperature.

As described above, the conventional printing apparatus with anautomatic double-sided printing function cannot avoid a variety ofproblems completely. That is, depending on the type of print medium, thekind of ink and whether the “full bleed printing” is executed, thequality of a printed image formed by the automatic double-sided printingvaries and the inner mechanisms of the printing apparatus are smeared.To cope with this situation, many of the currently available ink jetprinting apparatus capable of automatic double-sided printing areconstructed to allow a selection between a conventional, manualdouble-sided printing process and an automatic double-sided printingprocess using the automatic reversing unit. Thus, in performing thedouble-sided printing, the user must consider various conditions anddecide which printing process, manual or automatic, should be used. Thatis, the conventional problems, including troublesome steps and apossibility of erroneous insertion on the part of the user, are notavoided completely.

SUMMARY OF THE INVENTION

The present invention has been accomplished to overcome the aboveproblems and provide an ink jet print apparatus having a plurality ofdouble-sided printing modes, each of which using different transportpaths. It is also further object of this invention to provide an ink jetprint apparatus, an ink jet print method and a program, all of whichbeing capable of producing a sufficient image quality if any mode wouldbe executed.

In the first aspect of the present invention, there is provided an inkjet printing apparatus using a print head having print elements to ejectink to print an image on a print medium, the apparatus comprising;

a first double-sided printing mode to print on both surfaces of theprint medium; and

a second double-sided printing mode to print on both surfaces of theprint medium through a path different from that of the firstdouble-sided printing mode;

wherein the maximum volume of ink applied to a unit area of a printmedium for the first double-sided printing mode is smaller than that forthe second double-sided printing mode.

In the second aspect of the present invention, there is provided an inkjet print system using a print head having print elements to eject inkto print an image on a print medium, the system comprising:

a print image data generation means for converting image data to beprinted into print image data usable in a printing device having theprint head; and

an executing means to capable of executing a first double-sided printingmode to print on both surfaces of the print medium or a seconddouble-sided printing mode to print on both surfaces of the print mediumby using a path different from that of the first double-sided printingmode;

wherein the print image data generation means generates the print imagedata in one method when the first double-sided printing mode is executedand in another method when the second double-sided printing mode isexecuted.

In the third aspect of the present invention, there is provided an imageprocessing apparatus to generate a print image data used in a printingapparatus which can execute a first double-sided printing mode to printon both surfaces of a print medium by ejecting ink from a print head anda second double-sided printing mode to print on both surfaces of theprint medium using a path different from that used in the firstdouble-sided printing mode, including;

a converting means for converting image data to be printed on the printmedium into print image data be used in the printing apparatus;

wherein the converting means converts the image data so that an amountof ink applied to the print medium when the first double-sided printingmode is executed differs from that when the second double-sided printingmode is executed.

In the fourth aspect of the present invention, there is provided an inkjet print method using a print head having print elements to eject inkto print an image on a print medium, comprising the steps of:

selecting one printing mode from a plurality of printing modes, theprinting modes including a first double-sided printing mode capable ofprinting on both surfaces of the print medium and a second double-sidedprinting mode capable of printing on both surfaces of the printingmedium through a path different from that of the first double-sidedprinting mode;

converting image data to be printed into print image data to be used bya printing apparatus for printing according to the printing modeselected by the selection step; and

printing on the print medium by the print head according to the printimage data generated by the conversion step;

wherein the conversion step performs the data conversion so that anamount of ink applied to the print medium when the first double-sidedprinting mode is executed differs from that when the second double-sidedprinting means is executed.

In the fifth aspect of the present invention, there is provided aprogram for generating data which is used in a printing apparatus,wherein the printing apparatus comprising a print head having printelements to eject ink, a first double-sided printing mode capable ofprinting on both surfaces of a print medium, and a second double-sidedprinting mode capable of printing on both surfaces of the print mediumthrough a path different from that of the first double-sided printingmode,

the program being designed to cause a computer to execute the steps of:

deciding which of a plurality of printing modes, including the firstdouble-sided printing mode and the second double-sided printing mode, isto be executed; and

generating print image data to be used in the printing apparatus byconverting image data to be printed into the print image data in such away that an image is printed on the print medium at one print duty whenthe decision step decides to execute the first double-sided printingmode and at another print duty when the decision step decides to executethe second double-sided printing mode.

In the sixth aspect of the present invention, there is provided an inkjet print system using a print head having print elements to eject inkto print an image on a print medium, comprising:

a print image data generation means to convert image data to be printedinto print image data printable by the print head;

a first print medium transport means to transport the print medium forprinting; and

a second print medium transport means to transport the print mediumthrough a path different from that used by the first print mediumtransport means;

wherein the print image data generation means generates the print imagedata in one method when the first print medium transport means isoperated and in another method when the second print medium transportmeans is operated.

In the seventh aspect of the present invention, there is provided an inkjet print method to print an image on a print medium by a print headhaving print elements to eject ink to, comprising the steps of:

deciding which of a plurality of print medium transport means capable oftransporting the print medium through different paths in the process ofprinting on the print medium, is to be operated;

converting image data to be printed into print image data be used by aprinting apparatus to print according to the print medium transportmeans determined by the decision step; and

printing on the print medium by the print head according to the printimage data generated by the conversion step;

wherein the conversion step performs the data conversion so that anamount of ink applied to the print medium is adjusted in accordance withthe selected print medium transport means.

The above and other objects, effects, features and advantages of thepresent invention will become more apparent from the followingdescription of embodiments thereof taken in conjunction with theaccompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view showing a basic inner construction of anink jet printing apparatus applied to an embodiment of this invention;

FIG. 2 is a cross-sectional view of the printing apparatus applied tothe embodiment of this invention;

FIG. 3 is a schematic diagram showing the construction of an automaticdouble-sided printing unit applicable to the embodiment of thisinvention;

FIG. 4 is a block diagram showing an electric control configuration ofthe ink jet printing apparatus applied to the embodiment of thisinvention;

FIG. 5 is a flow chart showing a control flow when a printing operationis performed in Example 1;

FIGS. 6A to 6C show tables of output densities relative to an inputdensity (print duties) for three types of print medium; and

FIG. 7 is a flow chart showing a control flow when a printing operationis performed in Example 2.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

Now, an embodiment of the present invention will be described in detailby referring to the accompanying drawings.

(Basic Construction)

FIG. 1 is a perspective view showing a basic inner construction of anink jet printing apparatus 1 applied to this embodiment. FIG. 2 is across section of the printing apparatus 1 as seen from one side.

Referring to FIG. 1 and FIG. 2, the ink jet printing apparatus 1comprises mainly a paper supply unit 2, a feed unit 3, a discharge unit4, a carriage unit 5, and an automatic double-sided printing unit 9including a removable reversing unit. These components will be brieflyexplained one by one in the following.

(I) Paper Supply Unit

The paper supply unit 2 has mounted on a base 20 a pressure plate 21, onwhich sheets of a print medium P are placed, and a supply rotor 22 tosupply the print medium P. A movable side guide 23 is slidably mountedon the pressure plate 21 to restrict a mounting position of the printmedium P. The pressure plate 21 is rotatable about a rotating shaftconnected to the base 20 and biased toward the supply rotor 22 by apressure plate spring 24. At a portion of the pressure plate 21 facingthe supply rotor 22, a separation pad not shown which is made of amaterial with a large friction coefficient, such as an artificialleather, is provided to prevent a multiple sheet supply. The base 20 isalso provided with a separation claw not shown, a bank portion 27, aselection lever 28 and a release cam 29. The separation claw coverscorners of the print medium P at one end thereof and has a function ofseparating the print medium one sheet at a time. The bank portion 27 isformed integral with the base 20 to separate thick paper which cannot bedealt with by the separation claw. The selection lever 28 at a plainpaper position puts the separation claw into operation and, at a thickpaper position, takes it out of operation. The release cam 29 disengagesthe pressure plate 21 from the supply rotor 22.

In the above construction, during a standby state the release cam 29pushes down the pressure plate 21 to a predetermined position. So, thepressure plate 21 is disengaged from the supply rotor 22. In this statewhen a drive force of a transport roller 36 is transmitted through gearsto the supply rotor 22 and the release cam 29, the release cam 29 partsfrom the pressure plate 21 allowing the pressure plate 21 to rise. As aresult, the print medium P comes into contact with the supply rotor 22and can be picked up and supplied as the supply rotor 22 rotates. Theprint medium P is separated one sheet at a time by the separation clawand supplied to the feed unit 3. The supply rotor 22 and the release cam29 continue to rotate until the print medium P reaches the feed unit 3.When the print medium P has reached the feed unit 3, the release cam 29disengages the print medium P from the supply rotor 22, thus enteringthe standby state again. At the same time, the drive force from thetransport roller 36 is cut off.

(II) Feed Unit

The feed unit 3 has a transport roller 36 to transport the print mediumP and a PE sensor 32. A pinch roller 37 is held in contact with thetransport roller 36 so that it is rotated by the transport roller 36.

The pinch roller 37 is rotatably supported on a pinch roller guide 30.The pinch roller guide 30 is biased by a pinch roller spring to pressthe pinch roller 37 against the transport roller 36 to create atransporting force for the print medium P. At an inlet of the feed unit3 to which the print medium P is fed, an upper guide 33 for guiding theprint medium P and a platen 34 are arranged. The upper guide 33 isprovided with a PE sensor lever 35 that transmits a detection of frontand rear ends of the print medium P to the PE sensor 32.

In the above construction, the print medium P supplied to the feed unit3 is guided by the platen 34, pinch roller guide 30 and upper guide 33and fed to a roller pair of the transport roller 36 and the pinch roller37. At this time, the front end of the print medium P is detected by thePE sensor lever 35 and the detection information is used to determine aprint position of the print medium P. The print medium P is held betweenthe paired rollers 36, 37 driven by an LF motor not shown and therebytransported over the platen 34.

A print head 7 is a replaceable ink jet print head that has a removableink tank. The print head 7 has a plurality of print elements, eachprovided with an electrothermal transducer such as a heater. Energizingthe heater causes a film boiling in ink contained in each print element.A bubble produced in ink by the film boiling expands and contracts toproduce a pressure change and thereby eject an ink droplet from theprint element. The ink droplet thus ejected lands on the print medium Pto form a dot.

(III) Carriage Unit

The carriage unit 5 has a carriage 50 on which to mount the print head7. The carriage 50 is supported by a guide shaft 81, along which thecarriage 50 is reciprocally scanned in a direction crossing thetransport direction of the print medium P, and by a guide rail 82 thatholds the rear end of the carriage 50 to maintain a gap between theprint head 7 and the print medium P. The guide shaft 81 and the guiderail 82 are secured to a chassis 8.

The carriage 50 is driven through a timing belt 83 by a carriage motormounted on the chassis 8. The timing belt 83 is supported, with anappropriate tension, between idle pulleys 84. Further, the carriage 50has a flexible cable 56 to transmit a signal from a printed circuitboard to the print head 7.

In the above construction, when an image is to be formed on the printmedium P, the paired rollers 36, 37 feed the print medium P to a rowposition where an image is to be formed (a position in a transportdirection of the print medium P). At the same time, the carriage motor80 moves the carriage 50 to a column position where an image is to beformed (a position in a direction perpendicular to the transportdirection of the print medium P) to have the print head 7 face the imageforming position. Then, as the carriage 50 is moved, the print head 7ejects ink onto the print medium P according to a signal from theprinted circuit board to form an image.

Before mounting or dismounting the print head 7 to or from the carriage50 or mounting or dismounting an ink tank to or from the print head 7,the user presses an operation key not shown. This causes the carriage 50to move to a predetermined position where the user performs dismountingor replacement.

(IV) Cleaning Unit

The cleaning unit 6 has a pump 60 for cleaning the print head 7, a cap61 for preventing the print head 7 from drying, and a selection arm forswitching the drive force from the transport roller 36 between the papersupply unit 2 and the pump 60. During other than paper feeding andcleaning, the selection arm fixes a planetary gear (not shown), whichrotates about an axis of the transport roller 36, at a predeterminedposition so that its drive force is not transmitted to the paper supplyunit 2 or the pump 60. When the carriage 50 moves, the selection armfrees the planetary gear, allowing the planetary gear to move accordingto the forward or backward rotation of the transport roller 36. That is,when the transport roller 36 rotates forward, the drive force istransmitted to the paper supply unit 2; and when the transport roller 36rotates backward, the drive force is transferred to the pump 60.

(V) Discharge Unit

The discharge unit 4 has discharge rollers 41, 41A, a transfer roller 40that engages the transport roller 36 and the discharge roller 41, and atransfer roller 40A that engages the discharge roller 41 and dischargeroller 41A. The drive force of the transport roller 36 is thereforetransmitted through the transfer roller 40 to the discharge roller 41,from which it is further transmitted through the transfer roller 40A tothe discharge roller 41A.

Spurs 42, 42A are placed in contact with the discharge rollers 41, 41Aso as to be rotated by the discharge rollers 41, 41A. Further, acleaning roller 44 rotatably engages the spurs 42, 42A. In the aboveconstruction, the print medium P that was formed with an image by thecarriage unit 5 is gripped and transported between the discharge rollers41, 41A and the spurs 42, 42A and discharged onto a discharge tray 100.

Downstream of the discharge roller 41A there is a discharged papersupport 104 for supporting the discharged printed medium P. Thedischarged paper support 104 is pivotally mounted to a guide member 102.The guide member 102 supports the print medium P almost horizontallymovable between a position where the print medium P protrudes from theplaten 34 and a position where the print medium P is retracted onto theplaten 34. As the guide member 102 moves, the discharged paper support104 also pivots.

(VI) Automatic Double-Sided Printing Unit

FIG. 3 is a schematic diagram showing the construction of an automaticdouble-sided printing unit applicable to this embodiment.

The automatic double-sided printing unit 9 comprises a paper supply path94, the transport roller 36 and a reversing unit 90 installed behind theink jet printing apparatus 1. The reversing unit 90 is removable fromthe printing apparatus and, when it is mounted on the printingapparatus, the automatic double-sided printing unit 9 is formed.

The reversing unit 90 mainly comprises a paper holding roller 95, areversing small roller 92, a loop-shaped reversing path 93, and areversing large roller 91.

The transport roller 36 can be driven in the forward and backwarddirection by the transport motor. When the double-sided printing is tobe performed, the transport roller 36 is first rotated forwardly totransport the print medium P from the paper supply unit 2 toward thedischarge unit 4 to perform printing on a front surface (first surface)of the print medium P. After the printing is finished, the transportroller 36 is rotated backward to move the print medium P along the papersupply path 94 in the backward direction (from A to B) until the printmedium P enters the reversing path 93. Once the print medium P entersthe reversing path 93, the reversing small roller 92 and reversing largeroller 91 are rotated in the direction of arrows, moving the printmedium P along the transport path from B to C to E to F, with the resultthat the print medium P is turned upside down. After being turned over,the print medium P is transported along the paper supply path 94 again,this time in the forward direction (G direction) so that the backsurface (second surface) of the print medium P can be printed by theprint head 7. Then, the print medium P printed on both sides isdischarged onto the discharge unit 4.

As described above, in the automatic double-sided printing unit 9, theprint medium P passes through the reversing path 93 from A to B to C toE to F to G to complete the first/second surface inversion.

The outline construction of the ink jet printing apparatus applied tothis embodiment has been described with reference to FIG. 1 to FIG. 3.

FIG. 4 is a block diagram showing a configuration of an electric controlof the ink jet printing apparatus applied to this embodiment. In thisembodiment, the printing apparatus 1 and a host device 3000 together arereferred to as an ink jet print system.

In FIG. 4, reference number 2210 denotes an interface to transfersignals to and from the host device 3000. Through this interface 2210image information can be taken into the printing apparatus. Denoted 2214is an MPU, which, according to a program stored in a ROM 2212, performsa general control on the printing apparatus. Designated 2211 is a gatearray, and 2213 a DRAM capable of temporarily storing image informationfrom the gate array 2211.

Denoted 7 is a print head which is driven by a head driver 2215. Atransport motor 2219 is driven by a motor driver 2216 to transport apaper. A carriage motor 2220 is driven by a motor driver 2217 to movethe carriage.

In performing a printing operation, image data is received via theinterface 2210 and stored in the DRAM 2213. The stored image data isconverted for each line by the gate array 2211 from raster data into aprint image recordable by the print head 7 and then stored again in theDRAM 2213. The print image is then transferred through the gate array2211 to the head driver 2215, which drives the print head 7 according tothe received signal. The print head 7 causes a plurality of printelements of the associated rasters to eject ink according to the drivesignals to perform printing. The gate array 2211 has a print datacounter to count the number of printed dots.

The motor driver 2217 drives the carriage motor 2220 to move thecarriage mounting the print head 7 in the main scan direction. The scanspeed matches an ejection speed (ejection frequency) of the print head7.

The MPU 2214 performs an interrupt control on the gate array 2211 every10 msec to read an accumulated value of the counter. It then calculatesthe number of dots printed per unit time and determines a print duty fora unit area from a relation with the carriage scan speed.

After the carriage scan, which is performed while ejecting ink from theprint head 7, is completed for one line, the motor driver 2216 drivesthe transport motor 2219 to feed the print medium a predetermineddistance. By alternating the main scan of the print head and the subscanof the print medium as described above, an image is formed progressivelyon the print medium.

(Ink Characteristic)

The kind and characteristic of ink applied to this embodiment will beexplained as follows.

In the printing apparatus of this embodiment, a color ink tankcontaining a plurality of color ink and a black ink tank are removablymounted to the print head 7 so that they can be replaced independentlyof each other. It is noted, however, that this construction does notlimit this embodiment in any way. For example, a disposable type printhead formed integral with ink tanks of all colors may be used.

The print head 7 of this embodiment has a plurality of print elementsfor each of yellow, magenta, cyan and black ink. Color print elements(yellow, magenta and cyan) each eject about 5 ng of ink and black printelements about 3 ng of ink.

An example composition of each ink is described below.

1. Y (yellow) C.I. Direct Yellow 86  3% Diethylene glycol 10% Isopropylalcohol  2% Urea  5% Acetylenol EH (Kawaken Fine Chemicals Co., Ltd.) 1% Water 79% 2. M (magenta) C.I. Acid Red 289  3% Diethylene glycol 10%Isopropyl alcohol  2% Urea  5% Acetylenol EH (Kawaken Fine ChemicalsCo., Ltd.)  1% Water 79% 3. C (cyan) C.I. Direct Blue 199  3% Diethyleneglycol 10% Isopropyl alcohol  2% Urea  5% Acetylenol EH (Kawaken FineChemicals Co., Ltd.)  1% Water 79% 4. Bk (black) C.I. Direct Black 154 3% Diethylene glycol 10% Isopropyl alcohol  2% Urea  5% Water 80%

Acetylenol EH is a kind of surfactant that has an effect of improving apenetrability of ink. In this embodiment, only the color inks other thanblack are given 1% of Acetylenol EH and are therefore made penetrativeinks. In addition to Acetylenol EH, other surfactants and alcohols maybe used as additives for improving the ink penetrability. Improving theink penetrability in this way can facilitate the fixing of ink and thusprevent different color inks from bleeding and mixing together on aprint medium. However, an ink with an improved penetrability soaksdeeper and wider along fibers of the print medium, so an image(particularly character) quality degradation problem such as featheringmay occur. Therefore, in this embodiment, no additives such asAcetylenol EH are added to a black ink to realize a clear characterquality without feathering.

Although the inks listed above all use dyes as a colorant, othercolorants than dyes, such as pigments, may also be used.

If the double-sided printing is to be performed, the printing apparatusof this embodiment can choose between a mode in which the automaticdouble-sided printing unit is operated and a mode in which it is notused, as in the printing apparatus disclosed in the background artsection. However, the two modes provided in the printing apparatus ofthis invention differ from each other in a presence or an absence of theuse of the automatic double-sided printing unit but not just in it. Themost characteristic of this embodiment is that the double-sided printingimage data for these two modes are generated independently of each otherby different methods.

By referring to the drawings, the feature of this invention will beexplained in detail in a plurality of examples.

FIG. 5 is a flow chart showing a control flow in a printing process in afirst example. Here, a case is taken up, in which steps other thanStep-6, 9, 12 are performed by a printer driver in the host device andin which Steps-6, 9, 12 are performed by the printing apparatus. Thisexample is not limited to this configuration. All steps may be performedby the printing apparatus or only a part of other steps than Step-6, 9,12 may be performed by the printing apparatus.

In Step-1, print information to be used in actual printing is retrieved.Here, the print information may include, for example, information on thesize of print medium, an image quality, the type of print medium,whether a double-sided printing is performed, and whether the automaticdouble-sided printing unit (or the reversing unit) is used. Theseinformation can be set, for example, by the user on a printer driverinstalled in the host device.

In Step-2, a check is made to see if the double-sided printing isrequested. If it is decided that the double-side printing is to beperformed, the processing proceeds to Step-3.

Step-3 checks if the automatic double-sided printing unit (reversingunit) is to be used or not. If it is decided that the printing processrequires the use of the automatic double-sided printing unit (reversingunit), the processing moves to Step-4, where it sets an automaticdouble-sided printing mode. Step-5 generates print image data for theautomatic double-sided printing according to the setting made by Step-4.Then, Step-6 executes the automatic double-sided printing operationusing the print image data generated by Step-5. Now, this sequence isended.

If Step-3 decides that the printing process does not use the automaticdouble-sided printing unit, the processing moves to Step-7, where itsets a manual double-sided printing mode. Step-8 generates print imagedata for the manual double-sided printing according to the setting madeby Step-7. Then, Step-9 executes the manual double-sided printingoperation using the print image data generated by Step-8. Now, thissequence is ended.

If Step-2 decides that the printing process is not the double-sidedprinting, the processing proceeds to the Step-10, where it sets a normalprinting operation. At Step-11, print image data for the normal printingis generated according to the setting made by Step-10. Then, theprocessing moves to Step-12, where it executes the normal printingaccording to the print image data generated by Step-11. Now, thissequence is ended.

Here, the image generation performed by Step-5 will be explained. Step-5is a step to convert the image data to be printed into print data thatcan be printed by the printing apparatus. Normally, this step involvesconverting multi-valued image data into print data that preciselyrepresents the image and quantizing it. Since the print mode set byStep-4 determines a maximum volume of ink that can be applied to a unitarea of the print medium, Step-5 performs the conversion processing sothat the image formed does not exceed the maximum volume of ink.Similarly, Step-8 and Step-11 also perform the conversion processing sothat the image generation can be done without exceeding the maximum inkapplication volume of the associated print mode. The maximum volume ofink to be set for the automatic double-sided printing mode is smallerthan that to be set for the manual double-sided printing mode.

FIGS. 6A to 6C show tables of a real output density (print duty) of eachcolor with respect to a 100% input density (parameter) for three typesof print medium when Step-11, Step-8 and Step-5 generate print imagedata for the normal printing, manual double-sided printing and automaticdouble-sided printing. Suppose, for example, the printing apparatus ofthis embodiment prints an image with a resolution of 600 dpi(dots/inch). A printed state in which an ink drop is applied to everypixel in a predetermined area is represented as a 100% duty. Thus, asecondary color formed by overlapping two different inks has a maximumduty of 200% and a tertiary color formed by overlapping three differentinks has a maximum duty of 300%. In the ink jet printing apparatus ofthis embodiment, since the amount of ink ejected from each print elementis fixed, setting a print duty automatically determines the amount ofink applied to the print medium.

In the case of print medium 1, the normal printing performs a 100% dutyprinting with respect to the input parameter for primary colors ofblack, cyan, magenta and yellow.

In the manual double-sided printing, primary colors are printed at 100%except for black which is printed at 50%. Secondary and tertiary colorsare both printed at 200%. The reason that black is limited to 50% is tominimize an image quality degradation and smear that would otherwiseoccur when the double-sided printing is done using a black ink which hasa slow penetration speed. Further, for tertiary colors, the print dutyis reduced from 300% to 200% as a countermeasure against a print-throughvisible on print verso and curling during the double-sided printing.

In the automatic double-sided printing, primary colors are printed at75% and black at 30%, and secondary and tertiary colors are both printedat 150%. The black is limited to 30% to minimize an image qualitydegradation and smear that would otherwise occur when the double-sidedprinting is performed by the automatic double-sided printing unit usinga black ink which has a slow penetration speed. Further, for secondaryand tertiary colors, the ink application volume is reduced to 150% as acountermeasure against a print-through and curling during thedouble-sided printing using the automatic double-sided printing unit.

As described above, in this example the output print duty settingdiffers between the manual double-sided printing, the automaticdouble-sided printing and the normal printing. The reason that themanual double-sided printing and the automatic double-sided printing aregiven different output print duties is as follows.

In performing the manual double-sided printing, the user generallyperforms the printing and discharge processing continuously on aplurality of print medium sheets on only one surface (first surface).Then, the user turns over the discharged, stacked sheets, sets them inthe paper supply unit 2, and performs printing on the other unprintedsurface (second surface) for all sheets en masse. In this case, sincethe first and second surfaces of each sheet are printed at a relativelylong interval, it is highly likely that, by the time the second surfaceis printed, the ink applied to the first surface will already be fixedwell. In the automatic double-sided printing on the other hand, theprint medium sheet, after being printed on the first surface, is pulledinto the printing apparatus and turned over in the automaticdouble-sided printing unit for second surface printing. Thus, the firstand second surfaces of the same sheet are printed continuously at arelatively short interval. If a print duty is high, there is apossibility of the ink applied to the first surface not being fixed wellby the time the second surface is printed. Therefore, in thisembodiment, by setting the applied ink volume smaller in the automaticdouble-sided printing than in the manual double-sided printing, theproblems that are feared to arise during the automatic double-sidedprinting are resolved.

In the above, the black print duty is lowered in the manual andautomatic double-sided printing. This may result in a reduction in theblack character density. To deal with this problem, a tertiary colormade up of color inks, cyan, magenta and yellow, may be used to producea PCBk (Process Color Black) to replace or be added to the black imageportion. In this case, it is preferred that the print duty be set lessthan a value shown in a tertiary color column.

In either of the manual and automatic double-sided printing, the printduty of the overlay type black ink is set lower than those of thepenetrative color inks. This is because the overlay type black ink isnot as good as the penetrative color inks in terms of fixing and rubbingresistance characteristics and is more likely to induce a smear problem.

In the case of print medium 2, print duties for the normal printing areequal to those of the print medium 1. However, unlike the print medium1, the print medium 2 has the same print duty settings for the manualdouble-sided printing and the automatic double-sided printing. Here theprint medium 2 is assumed to have a characteristic that the rubbing andfixing problems have greater effects on the print quality than does theprint medium transport process of the automatic reversing unit. For sucha print medium, the above print duty settings reflects a fact that it isconsidered necessary to take positive countermeasures against therubbing and fixing problems and also a curling problem by reducing theprint duty for both the manual and automatic double-sided printingoperations.

In the case of print medium 3, no black ink is used. In this example,the print medium 3 is assumed to have a relatively glossy surface. For acombination of this print medium and the above inks, the rubbing andfixing problems are likely to occur with a black ink, so this exampleprints all black images using the abovementioned PCBk. However, the useof PCBk increases the ink application volume which in turn may cause acurling problem. Thus, this example allows the print duty to be reducedand set to an appropriate value in each of the manual and automaticdouble-sided printing to deal with these problems.

While three types of print medium have been described in the above, itis noted that the print medium is not limited to these. It is possibleto set the print duty at a lower than normal level for a print mediumthat is prone to curl and a print medium dedicated for double-sidedprinting.

As described above, in performing the double-sided printing, thisexample generates print image data for the manual double-sided printingand for the automatic double-sided printing independently of each otherby properly controlling print duties. More specifically, the handling ofthe print medium is selected according to a difference in the printmedium transport path in the printing apparatus, for instance, accordingto whether or not the print medium is passed through the automaticdouble-sided printing unit 9.

With this arrangement an ink jet printing apparatus is realized which,when the automatic double-sided printing unit is used, allowsdouble-sided printing to be executed automatically on a large number ofprint medium sheets at high speed without requiring any processing onthe part of the user and which at the same time can eliminate a numberof problems experienced with conventional printing apparatus, such asthe degradation of image quality, the contamination of interior of theprinting apparatus and the smudge problem, and thereby maintain a highimage quality during the double-sided printing.

This example described above can be applied to a broad scope of printmedium types. Particularly when postal cards and ink jet cards, whichare often printed on both sides, are used, the advantages of thisembodiment are enormous.

Next, a second example of this invention will be described.

This embodiment chooses a printing method best suited to a particulartransport process including a print medium supply, transport anddischarge (referred to as a paper path in this example) and generatesoptimum print data for that paper path. Consider a case, for example,where a double-sided printing is performed. A transport path (paperpath) taken when the print medium is supplied from ASF manually forprinting on one surface at a time differs from that taken when the printmedium is passed through the automatic double-sided printing unit forprinting on both surfaces. In a printing apparatus having multiple kindsof paper paths, this example generates image data that changes accordingto the paper path used.

FIG. 7 is a flow chart showing a flow of control in performing printingin this example.

First, at Step-71 information associated with actual printing (printinformation) is retrieved. The information associated with actualprinting includes, for instance, a print medium size, an image quality,a print medium type, whether or not double-sided printing is performed,and whether or not the automatic double-sided printing unit is used.These information can be set by the user on a printer driver installedin a host device.

Step-72 checks if the printing is to be performed through a paper pathA. In the printing apparatus of this example, two kinds of paper paths,A and B, are provided. If it is decided that the paper path A (e.g., atransport process using the automatic double-sided printing unit 9including the reversing unit 90) is used, the processing moves toStep-73. If it is decided that a paper path B (e.g., a transport processnot using the automatic double-sided printing unit 9) is used, theprocessing proceeds to step-76.

Step-73 makes a print setting for the paper path A. Step-74 generatesprint image data for the paper path A printing according to the settingmade by Step-73. Then, Step-75 executes the paper path A printingaccording to the print image data generated by Step-74. Now, thissequence is ended.

Step-76 on the other hand makes a print setting for the paper path B. AtStep-77, print image data for the paper path B printing is generatedaccording to the setting made by Step-76. Then, Step-78 executes thepaper path B printing according to the print image data generated byStep-77. Now, this sequence is ended.

When Step-74 and Step-77 generate print image data for the paper path Aand paper path B, respectively, a correspondence table of FIGS. 6A to 6Cor its equivalent representing a relation between a 100% input densityand a real output density (print duty) for each color can be applied, asin Example 1. When the correspondence table of FIGS. 6A to 6C areapplied, it is preferred that the print duties in a row of the automaticdouble-sided printing be used for the path A and those in a row of themanual double-sided printing for the path B. In the case of paper path Ain which the print medium is transported through the automaticdouble-sided printing unit 9, a relatively short period of time afterone of its surfaces has been printed, the print medium is transported tothe automatic double-sided printing unit 9 where it is turned upsidedown. This means that the printed surface will contact the transportpath in a relatively short time. Therefore, when the path A is used, theprint duties need to be set relatively low.

In the case of paper path B in which the print medium is transportedwithout being passed through the automatic double-sided printing unit 9,the print medium, after one of its surfaces has been printed, isdischarged out of the printing apparatus. In a one-sided printing, theprinted surface will not contact the transport path. Even in thedouble-sided printing, the only time that the printed surface contactsthe transport path is when it is supplied again into the printingapparatus. So, the time it takes for the printed surface to contact thetransport path is relatively long. This means that in the case of paperpath B, the print duties can be set relatively higher than those ofpaper path A.

While we have described an example printing apparatus having two kindsof paper paths, A and B, this invention is of course effective if threeor more paper paths are provided.

In a printing apparatus having a plurality of paper paths, this examplegenerates print image data for each of the paper path independently toproperly control the print duty according to the selected paper path.This makes it possible to provide an ink jet printing apparatus thatstably maintains a high image quality whichever paper path is chosen.

Different paper paths taken when the automatic double-sided printingunit is used and when it is not, have significantly differing influenceson an image quality. It is therefore effective to provide an appropriateprint medium handling by adjusting the print duty and generating printimage data according to a selected print medium transport process in theprinting apparatus, e.g., according to whether or not a paper pathrunning through the automatic double-sided printing unit is used.

This example described above can be applied to various types of printmedium, as in Example 1. Particularly when postal cards and ink jetpostal cards, which are often printed on both sides, are used, theadvantages of this example are enormous.

With this example, it is also possible to deal with variations in paperpaths, which occur not only according to whether or not the automaticdouble-sided printing unit described in Embodiment 1 is used but alsowhen different kinds of automatic reversing units are employed or when aone-sided printing is provided with different paper paths. This in turnallows problems of rubbing, ink fixing, smear and curling to be dealtwith more reliably, providing a printing system free from imageproblems.

Implementing the present invention in the form of the above two examplescan produce a stable image quality without causing troubles experiencedwith the conventional printing apparatus, whichever transport process ischosen during printing. The user can use the automatic double-sidedprinting unit without regard to problems that may occur withconventional printing apparatus when a print medium prone to a curlingproblem is used, when an overlay type ink is used, when a “full bleedprinting” is performed, or when printing is done under a variety ofconditions including ambient temperature and humidity.

Although the embodiments of this invention have been described as an inkjet print system having the printing apparatus 1 externally connected tothe host device 3000, as shown in FIG. 4, this invention is not limitedto this configuration. For example, the external device to which theprinting apparatus is connected is not necessarily a host device but maybe digital cameras and other information devices.

Further, while the print image data may be generated by a printer driverinstalled in the host device 3000, it may also be generated by theprinting apparatus 1. If the print image data is generated by theprinter driver in the host device, the print image data is transferredto the printing apparatus, which then performs printing according to theprint image data.

Further, rather than a configuration in which the printing apparatus isexternally connected to an information device, this invention is alsoeffectively applied to a configuration in which all controls areperformed by a totally integrated ink jet print system.

Further, in the above examples, the method of controlling the print dutyhas been described as an example means to adjust the amount of inkapplied to the print medium. This is an effective method particularlywhen the ink volume ejected from each print element is fixed to apredetermined volume as in the ink jet printing apparatus of thisembodiment. However, in this embodiment, the means to adjust the amountof ink applied to the print medium is not limited to the aboveconfiguration. For example, when an ink jet printing apparatus is usedthat can modulate the ink volumes ejected from the individual printelements, the amount of ink applied to the print medium can be adjustedby modulating the print element ink ejection volumes or by combining thecontrol of the print duty with the modulation of the print element inkejection volumes.

In the above embodiments while the reversing unit 90 has been describedto be mountable on the printing apparatus, it may be formed integralwith the printing apparatus. In that case, the automatic double-sidedprinting unit 9 is incorporated in the printing apparatus.

Further, this invention can be applied either to a system comprising aplurality of devices (e.g., host computer, interface device, reader,printer, etc.) or to an apparatus comprising a single device (e.g.,copying machine and facsimile).

The scope of this invention further includes the followingimplementation. That is, an apparatus or system connected to a varietyof devices incorporates a computer (CPU or MPU), which is loaded withsoftware program codes and runs the program to operate the devices torealize various functions of the above embodiments.

In that case, the software program codes themselves realize thefunctions of the above embodiments. Thus, the program codes and a meansto supply the program codes to the computer, for example a storage mediastoring the program codes, together constitute the invention.

Storage media for storing the program codes may include, for example,floppy disks, hard disks, optical discs, magnetooptical discs, CD-ROMs,magnetic tapes, non-volatile memory cards and ROMs.

The program codes are included in the embodiment of this invention notonly when the functions of the above examples are realized by thecomputer executing the supplied program codes but also when the programcodes cooperate with an operating system running on the computer or withother application programs to realize the functions of the aboveembodiments. For example, program codes corresponding to at least a partof the flow charts of FIG. 5 and FIG. 7 are included in the scope ofthis invention.

The present invention has been described in detail with respect topreferred embodiments, and it will now be apparent from the foregoing tothose skilled in the art that changes and modifications may be madewithout departing from the invention in its broader aspect, and it isthe intention, therefore, in the apparent claims to cover all suchchanges and modifications as fall within the true spirit of theinvention.

This application claims priority from Japanese Patent Application No.2003-290734 filed Aug. 8, 2003, which is hereby incorporated byreference herein.

1. An ink jet printing apparatus using a print head having printelements to eject ink to print an image on a print medium, the apparatuscomprising: a first double-sided printing mode to print on both surfacesof the print medium; and a second double-sided printing mode to print onboth surfaces of the print medium through a path different from thatused in the first double-sided printing mode, wherein the maximum volumeof ink applied to a unit area of a print medium in the firstdouble-sided printing mode is less than that in the second double-sidedprinting mode.
 2. An ink jet printing apparatus according to claim 1,wherein the first double-sided printing mode is executed to print on onesurface of the print medium and then to print on another surface of theprint medium, without discharging the print medium.
 3. An ink jetprinting apparatus according to claim 1, wherein the first double-sidedprinting mode is executed to perform printing according to print imagedata generated in such a manner that the maximum volume of ink appliedto a unit area in the first double-sided printing mode is less than thatin the second double-sided printing mode.
 4. An ink jet printingapparatus according to claim 3, wherein the first double-sided printingmode performs an automatic double-sided printing in which, after aprinting operation is carried out on one surface of the print medium,the print medium is turned over automatically in the printing apparatuswithout discharging the print medium, and then the printing operation iscarried out on another surface of the print medium, and wherein thesecond double-sided printing mode performs a manual double-sidedprinting in which, after a printing operation is carried out on the onesurface of the print medium, the print medium is discharged from theprinting apparatus, and then the printing operation is carried out onthe other surface of the print medium supplied into the printingapparatus by a user.
 5. An ink jet print system using a print headhaving print elements to eject ink to print an image on a print medium,the system comprising: print image data generation means for conveningimage data to be printed into print image data usable in a printingdevice having the print head; and executing means capable of executing afirst double-sided printing mode to print on both surfaces of the printmedium or a second double-sided printing mode to print on both surfacesof the print medium by using a path different from that used in thefirst double-sided printing mode, wherein the print image datageneration means generates the print image data by one method when thefirst double-sided printing mode is executed and by another method whenthe second double-sided printing mode is executed.
 6. An imageprocessing apparatus to generate print image data used in a printingapparatus which can execute a first double-sided printing mode to printon both surfaces of a print medium by ejecting ink from a print head anda second double-sided printing mode to print on both surfaces of theprint medium using a path different from that used in the firstdouble-sided printing mode, comprising: receiving means for receivingimage data to be printed on the print medium; and converting means forconverting the received image data to be printed on the print mediuminto print image data used in the printing apparatus, wherein theconverting means converts the image data so that an amount of inkapplied to the print medium when the first double-sided printing mode isexecuted differs from that when the second double-sided printing mode isexecuted.
 7. An ink jet print method using a print head having printelements to eject ink to print an image on a print medium, comprisingthe steps of: selecting one printing mode from a plurality of printingmodes, the printing modes including a first double-sided printing modecapable of printing on both surfaces of the print medium and a seconddouble-sided printing mode capable of printing on both surfaces of theprinting medium through a path different from that used in the firstdouble-sided printing mode; converting image data to be printed intoprint image data to be used by a printing apparatus for printingaccording to the printing mode selected in the selecting step; andprinting on the print medium with the print head according to the printimage data generated in the converting step, wherein the convening stepperforms the data conversion so that an amount of ink applied to theprint medium when the first double-sided printing mode is executeddiffers from that when the second double-sided printing mode isexecuted.
 8. An ink jet print method according to claim 7, wherein thefirst double-sided printing mode performs an automatic double-sidedprinting in which, after a printing operation is carried out on onesurface of the print medium, the print medium is turned overautomatically in the printing apparatus without discharging the printmedium, and then the printing operation is carried out on anothersurface of the print medium, and wherein the second double-sidedprinting mode performs a manual double-sided printing in which, after aprinting operation is carried out on the one surface of the printmedium, the print medium is discharged from the printing apparatus, andthen the printing operation is carried out on the other surface of theprint medium supplied into the printing apparatus by a user.
 9. An inkjet print system using a print head having print elements to eject inkto print an image on a print medium, comprising: print image datageneration means to convert image data to be printed into print imagedata printable by the print head; first print medium transport means totransport the print medium for printing; and second print mediumtransport means to transport the print medium through a path differentfrom that used by the first print medium transport means, wherein theprint image data generation means generates the print image data by onemethod when the first print medium transport means is used and byanother method when the second print medium transport means is used. 10.An ink jet print method to print an image on a print medium by a printhead having print elements to eject ink, comprising the steps of:deciding which of a plurality of print medium transport sections,capable of transporting the print medium through different paths in theprocess of printing on the print medium, is to be operated; convertingimage data to be printed into print image data to be used by a printingapparatus to print according to the print medium transport sectionsdetermined in the deciding step; and printing on the print medium withthe print head according to the print image data generated in theconverting step, wherein the converting step performs the dataconversion so that an amount of ink applied to the print medium isadjusted in accordance with the selected print medium transport section.